V8 MC1 to Pre-Alpha (1977-1982) interchangeability

[jones01m]

I am sure this question has been posed before, so please forgive me in advance. I have searched the forum quite a bit, and also have the Alpha outdrive version history put together by Don S ? this information is very much appreciated by the way.

I currently have a 1976 Mercruiser 888. This gimble assembly is the type with the nails in the gimble ring. It also has the round spline that connects to the ring, which is worn and concerns me from a safety aspect so I want to replace it. I am looking at ebay and craigslist for replacement parts. My goal is to pick up the whole outer transom assembly (Outer plate, gimble ring, bell). I am pretty sure I understand the outdrive interchangeability issues.
So here are my questions:

1. Will the 1977-1982 assembly bolt right up with my inner transom plate?
2. What year did the inner transom plate lugs change in width for the V8?
3. Is the outer transom assembly always different between V8 and 6/4cyl versions? I am only interested in the V8 version and I want my 302 with y-pipe to bolt up properly.
4. If the answer to #1 is yes, does it matter what V8 was originally bolted up (Chevy/Ford?) engine size?

Thank you in advance for your responses.

I am already aware of the complete drive train upgrade option with a donor boat.

 

[Bondo]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

So here are my questions:

1. Will the 1977-1982 assembly bolt right up with my inner transom plate?
2. What year did the inner transom plate lugs change in width for the V8?
3. Is the outer transom assembly always different between V8 and 6/4cyl versions? I am only interested in the V8 version and I want my 302 with y-pipe to bolt up properly.
4. If the answer to #1 is yes, does it matter what V8 was originally bolted up (Chevy/Ford?) engine size?

Ayuh,.... 1,... Ya it Should,....
2,... 'bout '82/ '83 or so,....
3,... Not certain, but I doubt yer y-pipe is gonna be swap friendly,... 4- 6- V8 shouldn't matter...
4,... Don't believe so...

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

Thank you sir.

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

Thank you sir.

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

So I am sorry I didn't see the below attached thread prior to posting.

I have one more specific question: Can I use a post 1982 gimbal bearing housing and bolt up to the inner transom plate? I can't seem to verify if the exhaust pipe mount would be the same and plate thru-bolt pattern. The only reason I would keep the inner transom assembly is becuause of the engine mount change in 1983.

302 - mc1 inner transom plate - R/MR/Alpha1 gimble bearing housing??? possible?
I will keep my y-pipe.



http://forums.iboats.com/showthread.php?t=536809&p=3674872#post3674872

 

[Bondo]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

I can't seem to verify if the exhaust pipe mount would be the same and plate thru-bolt pattern. The only reason I would keep the inner transom assembly is becuause of the engine mount change in 1983.

Ayuh,... Like I said, I ain't so sure, but I believe yer y-pipe ain't gonna like the swap,...
You've got the 3 piece y-pipe, Right,..??
I believe the lower connection at the transom housing is a different bolt pattern,...

I also donno if yer risers will align with a newer y-pipe...

The inner plate bolt pattern oughta be the same,... at worse, abit of tunin' with a die-grinder might be needed....

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

Thanks for your time Bond-o.
I spent many more additional hours last night sifting through part numbers and pictures on line.

Here is some additional information I found.

- The 6 and 4 cyl gimbal housing assemblies will not work with V8 (exhaust fit up issues)
- The 1983 and later V8 gimbal housings also will not work becuase of the exhaust fit up issues. If I was to use the post 1983 y-pipe with my 302 and existing inner transom assembly then I start running into issues with alignment at my engine exhaust elbows.
- The gimbal ring appears to be interchangeable all the way through the alpha1 models.
- One needs to be aware of the square stering arm attachment for later models.
- It is desired to have the square gimbal ring attachment in the assembly (requirement for me)

So this is what I will get: An outer transom assembly between the dates of 1976-1982 with a square feature on the gimbal ring. The drive arm will have the round spline. It must come from a V8 and I can check that I have what I need by looking at the exhaust configuration in pictures (you get this right - you have what you need).

The distinguishing feature on the exhaust port is the oval hole with to round ports below surrounded by O-rings (pre-1983)
The 1983 and above has stretched ports below the exhaust port and uses a single serpantine type O-ring seal.

Be careful on the years. My boat is a 1976 and everything about the documentation I found on-line says the gimbal assembly is a 1975.

So... in the end... pretty much what Bond-o has already said.

Iboats Forum again has pointed me in the right direction. Thank you.

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

So... there is a bit more to the story...

I just receive my outer transom assembly (outer plate, gimble ring, bell) from an ebay purchase.
This unit appears to be much more robust than the pre-1976 mc1, but there is one fit-up issue: The top two through-transom bolts are higher, but the bottom four match up perfect along with the other features. I will document the exact differences on this thread with photos. Until then, I am in search of the mating inner transom plate.

 

[geneseo1911]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

Thank you for updating this, jones. I'm struggling with similar issues, and the question of which gimbal housings mate to which transom plates to which gimbal rings seems to be a bit of a dark art-not much good info around.

 

[Fordiesel69]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

Another option you could consider, online there is a place that will weld up your holes and remachine to make them tight again. Of course this means you would be without a boat, but for $80 per hole it would be cheaper and less labor involved. This of course just an opinion.

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

geneseo1911, No problem I will continue to update until she is installed and add some photos to document my findings.

Fordiesel69, Man if you can believe it I got a complete outer assembly off of ebay for $91 and the inner transom plate for $90 (purchased minutes ago). I had to be patient, but it eventually came up.

 

[jones01m]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

I have a bit more information to help decipher this puzzle.
There are really three notable differences in the pre-1976 and the 1976-1982 innner transom plates: Enlarged hole for water intake, vertical distance between through bolts, and position of the limit switch wire hole.

The more modern transom assembly has a distance between bolt of approximately 5-11/16"

Older version screw distance is 5"

When looking for a new assembly look for the signature split in the top of the gimble ring - this is the updated version

This conversion requires repositioning of the top through holes in the transom and some additional sanding on the sides of the main cutout.

 

[geneseo1911]

Re: V8 MC1 to Pre-Alpha (1977-1982) interchangeability

That is an excellent post. Have you looked into the differences between the 76-82 plates and the alpha 1 gen 1? I think you said the exhaust became an issue there, but everything else should be the same. Sounds like a question only through-hulls can answer...